I just uploaded a new version. Download it from the link above, or here. New features:

[*:3g2u7b0t]Flood with lava instead of water
[*:3g2u7b0t]More randomness to the terrain height and type of mountains
[*:3g2u7b0t]Paint the terrain with different materials (dirt, sand, stone, water, lava, etc...)

There are new buttons along the bottom of the window to select the terrain type you want to paint with the "Paint Terrain" tool. A number of actions have been moved to the File menu (creating a new world, loading, saving and exporting worlds).

This already worked in the previous version, but it's not obvious so I though I would point it out: although there is no Undo functionality, for some tools you can right-click instead of left-click to do the opposite. For instance, right clicking with the "Frost Paint" tool selected will remove the frost, and right-clicking with the "Raise Mountain" tool selected will dig a hole instead. Right-clicking with "Paint Terrain" selected will restore the terrain type to the default.

Also, use the scroll wheel to change the radius, and middle-click and drag to move the map.

Hmmm, I have no idea why that would happen. Could you try out the new version, see if anything has changed? If it still doesn't work, please PM me as many details as possible (what is your operating system? From which directory are you running it? How are you running it? Double clicking? Command line? Also, please run it from a command line and let me know what it prints there).

Tried this yesterday, and it is a great program! I hope to see it continue to develop, and get better.
There was a couple of features I noticed were missing, that I would have liked to see. The first thing, it that, though you can raise the land, and the water levels up, there is no way to lower them again, not directly anyways. You can use the Flatten feature to accomplish this, but an option to lower a specific section would work better. For instance, If I were to generate an island, and wanted a low spot in the middle, I would have to raise several mountains in a circle, then use the flatten feature to smooth them a bit, but the middle may not be at the desired height, or if one raises a mountain too high, it is a bigger pain to "flatten" it, than to simply lower it. Lowering the water, after flooding, would be a nice feature as well, especially if you want a dry area, that is lower than the water level.
The other feature I would like to see, is the option to make the water level the same as the rest of the world. By this I mean, you had already mentioned about the new chunks spawning on their own when you explore far enough, and if you miscalculate the water level in the area you created, it does not match up to the rest of the world, thus making it look out of place. I'm not trying to be critical, as I love the program, but these additions, I think, would make it a bit more user-friendly.

This is amazing! One thing I do miss is an ability to draw squares and to lower the terrain. Does this update automatically? If not, can you make it do so and PM me when you have? Thanks for this awesome program!

Very intuitive. I was able to download it, open it, and immediately get to work, without having to read any sort of manual, instructions, or readme. I love this program, and can't wait for future improvements.

YES. this is amazing. i truly love this. i just have one question, this saves files as .world yet i want files saved as .dat for my server... is it possible to convert them? i run on a mac, if that even matters. thanks again!

YES. this is amazing. i truly love this. i just have one question, this saves files as .world yet i want files saved as .dat for my server... is it possible to convert them? i run on a mac, if that even matters. thanks again!

well, this is simply bizarre.
I've been tinkering with this thing trying to get it to work. Trying the different suggestions.

I've tried command line, double clicking, right-click then "open with" all spit the error at me.
I grabbed my neighbors little netbook and dl the program, install java on his machine, run Worldbuilder from command line and it runs fine. Works fine double clicking too.

So I gave up, went and had dinner. Came back. downlanded the file just incase, used the command line and it works fine now. Still errors on export with double clicking and "open with".

But the landscape that I'd made with the erroring one now blows up when i load it. lol no biggy, I wasn't that far.

I uploaded a new version of the program. It has the following new features:

[*:2g3beiuq]"Up" in the tool is now "north" in the game, and the displayed coordinates match those of the game
[*:2g3beiuq]Much better smoothing of the actions of the operators (at the cost of increased memory use).
[*:2g3beiuq]Terrain raise / lower operator. Left-click raises, right-click lowers.
[*:2g3beiuq]Terrain smoothing operator. Very slow, use with a small radius!
[*:2g3beiuq]The water/lava level and depth are now indicated in the status bar.
[*:2g3beiuq]Everything should now be accessible with keyboard commands. Use alt plus the underlined letter to select operators and terrain types (the buttons on the toolbars), use - and + to change the radius.

Unfortunately the changes for the smoother operation necessitated a new save file format, so you can't load files saved with the previous version any more. Sorry about that. From now it should not be necessary any more to change the file format.

There is no undo yet, and I'm not sure if I will implement it at all, because it would be slow and use huge amounts of memory. But we'll see. Save early, save often... ;-)

@Chr0nos: you can now see what the water level is in the status bar, which should make it easier to make the water level match that of the surrounding blocks (which is at 64). Also, you talk about lowering the water, you know you can already do this by right-clicking with the flood tool selected, right? Although I admit it is a pain in the ass to drain every individual lake and puddle which is created if you flood too high.

With the problem I was having i forgot an important thing... Thank you for making this awesome tool. It's fantastic and I'm very impressed. Even in it's testing state I'm very happy with the results I've gotten. Amazing work, thanks again!

This is awesome. How large will the maps it creates be able to be, at release or further on in testing?

Extremely large. I've tested it with 25 by 25 tiles (a tile is 8 by 8 chunks, or 128 by 128 blocks, so that makes a total of 3200 blocks or 3.2 km (2 miles) a side). If you have plenty of memory (you may have to start the program from the command line with something like java -Xmx1024M -jar WorldPainter.jar to make it available to the program) I think you can go much larger still, although I haven't tested that myself yet.

Update: I just did a little test. I generated a world of 50 by 50 tiles (6400 by 6400 blocks or four by four miles). It took a couple of seconds to generate, and exporting it took a couple of minutes, but otherwise it worked fine. The resulting map size on disk was about 600 MB, and the Java memory usage was about 350 MB. The .world file was about 60 MB. I'm sure I could go much larger still... :-)